In the field of analytics there is a great demand for fluid devices and in particular capillary paths for transporting e.g. fluids by means of capillary forces, for examining them while they are being transported or for producing sample receptacles in which the fluids stand and the surfaces of which are treated with chemical substances so that specific sample fluids will undergo a reaction with these substances, said reaction causing e.g. a change in colour of these sample fluids. In order to be able to detect such a change in colour of a sample fluid, or in order to be able to detect the optical properties of a sample fluid in general, it is important that fluid devices are transparent on both sides so that analyses can be carried out in transmitted light, e.g. by making use of fluorescent properties.
Capillary paths are nowadays used in a great variety of technical fields, e.g. in the field of chemical analytics and biochemistry. Such capillaries are etched into silicon wafers and then provided with a cover and thus closed. Although a glass cover can be used for closing such silicon-etched wafers, a substrate wafer, which is normally not optically transparent, is provided on the back, i.e. on the other side of the capillary path. Hence, such capillary paths are not suitable for transmitted-light analyses. In order to be actually able to carry out optical analyses with such capillary paths, it is necessary to apply e.g. a metal layer to the silicon-etched fluid structures, so that a reflection analysis can be carried out. In addition to the fact that such capillary paths are not suitable for transmitted-light determinations, the application of a mirror coating to the silicon is a further production step, which is complicated and which increases the costs for the fluid device.
In addition, it is difficult to adjust precise depths of the fluid structure by means of etching methods. It is true that very precisely controllable amounts of material can be removed by dry-etching techniques, but these techniques are disadvantageous insofar as the etching parameters must be controlled very precisely; this, in turn, results in high production costs for such capillary components. If the etching parameters are not strictly controlled in this way, a high reject rate will occur in the production process.
Especially in the field of analytics, disposable analysis elements are used to an increasing extent. Hence, fluid devices become more and more mass-produced articles. Especially mass-produced articles should fulfil the requirement of being economy-priced. It follows that even small differences in prices will have the effect that one product will gain more acceptance on the market than another. Only economy-priced fluid devices are therefore competitive.